Conversion of hydrocarbon oils



Filed Oct. 31, 1954 2 Sheets-Sheet 1 I N V EN TOR. HAROLD MATWELL BY LOW J? )4m,a

A TTORNEY 2 Sheets-Sheet 2 H. v. ATWELL CONVERSION OF HYOROCARBON OILS Filed Oct. 51, 1934 Jan. 26, 1937.

Patented flan. 26, 1937 UNITED STATES [PATENT OFFICE CONVERSION OF HYDRjOOABBON OILS Hamid V. Atwell,

Process White rum, N. 1., assignor to Management Company,

Inc., New

York, Y., a corporation-of Delaware application Qctober 31, 1934, Serial No. 750,856

This invention relates to conversion of hydrocarbon oils and pertains more particularly to a process of cracking hydrocarbons wherein inter-' mediate products of an initial cracking operation 'are treated in \a more effective and eflicient provement in the quality of products produced.

My invention in its entirety constitutes a series of steps and combination of steps for accomplishing the above and other objects.

For a clear understanding of the objects and nature of my invention reference is now made to the accompanying drawings in which:

Figure 1 is a diagrammatic and schematic plan view of a portion of an apparatus suitable for carrying my invention into effect, and

Figure 1A is a similar view of the remaining portion of the apparatus.

Referring to Figure 1 of the drawings, the numeral ill desfgnates a charging line having a pump ii for introducing the oil to be treated into the system. 'I'lriis charging oil should be a relatively clean stock, such as 35 A. P. 1. gas oil from a paramn or mixed based crude which is suitable for drastic crackingtreatment for maximum conversion into gasoline constituents. The charging stock before being passed to the cracking zonemay be'heated to any desired degree by heat exchange with hot products of the system. For example, it will be of advantage to pass the fresh oil through one or both of the heatexchangers i2 and I3, through pipe lines l4, l5, and l6, l1 respectively, wherein the oil is preheated by products from a distilling operation .to be hereinafter described.

The fresh charging oil with or without preheating in one or both of the heat exchangers i2 and i3 is passed through line It) to a. heatsure at the outlet of. the coil'may range from x500 to 1000-or more pounds per square inch.

(on. lac-so) The hot cracked products after being sub- Jected to the desired heat treatment within the heating coil it are discharged through the transfer line it into a separating chamber where= in liquid and residual products separate. The temperature of the products in transfer line 19" is preferably lowered below cracking temperature by introducing a relatively cooler oil into the stream through line 2! before introducing the same into the separator 20. The separator 20 is also preferably maintained at materially lower pressure than the coil outlet pressure and to this end the line it is provided with a reducing valve 22. For example the pressure in the separator 26 may vary from atmospheric to 300 pounds persquare inch. If desired a soaking drum (not shown) may be provided between the heating coil i8 and the separator 20. The charging stock is preferably maintained within the cracking zone for a period sufficient to effect a relatively high percentage conversion in gasoline constituents. For example, the aniount of conversion of the original charging stock into gasoline constituents during a single passage through the cracking zone may range from to 40 percent or more of the original charge depending upon the character thereof.

The unvaporized residual products separated within the separator 20 are withdrawn from the bottom thereof through line 23 and, in accordance with one phase of my invention, will preferably be subjected to additional treatment as hereinafter described.

Vapors liberated within the separator 20 pass through line 24 to a fractionating tower 25 and are subjected to fractional condensation therein. The temperature of the tower 25 is controlled so as to condense the .vapors higher boiling than the desired motor fuel products produced from the cracking operation. For example, the temperature of the products at the bottom of the tower may range from 650 to 725 F. and the outlet temperature at the top of the tower may range from 350 to 450 F. To this end the tower 25 will be provided with cooling and fractionating elements 28 such as bubble trays, disc and doughnutbailles, cooling coils, et cetera. The pressurehlimaintained within the bubble tower may correspond to that maintained within the separator 20, except for the required drop to maintain. the desired flow of vapors. I prefer, however, to maintain a substantial pressure such as, for example, to 200 or more pounds per square inch. v a

. ing through heat exchangers 30, 3| and 32 may Vapors remaining uncondensed within the fractionating tower 25 and which include the desired gasoline constituents pass overhead through line 21 to a condenser 28 (see Figure 1A) wherein the gasoline constituents are condensed.

The condensate formed in the tower 25 may be withdrawn from the bottom thereof through line 29 and a part or all of the condensate after passbe introduced into a solvent extractor 33 and treated as hereinafter described.

However an intermediate trap-out tray 34 may be provided in the tower 25 for separately collecting a lighter condensate fraction. This fraction may be in the nature of kerosene or furnace oil and may be withdrawn from the trap-out tray through'line 35 and removed from the system. The condensate passing through the heat exchangers 30 and 3| pass in heat exchange relation with products from the solvent extractor 33, as hereinafter described. Heat exchanger 32 may be provided with lines 36 and 31 for introducing an extraneous medium to further cool the condensate before introducing the same to the ex tractor 33. The heat exchangers 30, 3!, and 32 are preferably of the counter-flow type in which the cooling medium passes countercurrent to the flow of the condensate. For simplicity the heat exchangers have been shown merely diagrammatically with the understanding that any suitable type may be employed.

The condensate before being introduced into the solvent extractor 33 should be cooled somewhat below the boiling point of the lighter solvent employed in the solvent extractor 33 as will 7 be more fully explained hereinafter.

The condensate upon being introduced into the solvent extractor 33 is caused to cont-act'with a solvent or solvents and preferably a solvent and an antisolvent capable of separating the condensate into two separate fractions differing from each other in chemical composition; one fraction of which will consist principally of para-iiinic hydrocarbons and the other fraction of which will consist principally of nonparaifinic hydrocarbons.

The term paraffinic wherever employed in this application is intended to refer -to saturated straight and branched chain hydrocarbons, and the term nonparaflinic as herein employed is intended to refer to unsaturates and cyclic compounds such as naphthenes and aromatic compounds.

It is preferred to treat the condensate with a solvent or mixture of solvents having a relatively high solvent power for nonparaffinic constituents and a relatively low solvent power for.paraffinic constituents. I For example, solvents such as dichlor, di-ethyl-ether, furfural, nitrobenzene, sulfur dioxide, phenol, polyhydric alcohols, such as glycerol .and ethylene glycol and numerous other oxygenated and chlorinated organic compounds are suitable for this purpose.

In addition to using a solvent of the above character it is also preferred to introduce into the solvent extractor 33 an antisolvent or precipitating agent which'may or may not function as a true solvent but which, by increasing the paraffinicity of the material treated, by stripping action, by precipitating action or in some other manner, will aidin effecting a better separation of parafiinic and nonparaflinic components of the condensates. For example, light liquid normally gaseous hydrocarbons such as ethane, propane and butane, and mixtures thereof, may be employed for this purpose. A suitable product may be obtained from a trap-out tray located in the top of a pressure stabilizer used for stabilizing gasoline. Such a product will usually consist principally of propane with small percentages of ethane and butane. For example, a light liquid product from the top of stabilizer 38 (see Figure 1A), which is used for stabilizing gasoline produced as a result of the cracking operation hereinbefore described, may be employed for this purpose.

For convenience I haveshown the solvent extractor 33 of the countercurrent type wherein the lighter liquid hydrocarbon antisolvent or precipitating agent is introduced into the bottom thereof through line 39 and the nonparaflinic solvent is introduced into the top thereof through the line 40, whereas the condensate is introduced into an intermediate section of the extractor.

The condensate upon being subjected to solvent treatment within the solvent extractor 33 separates into a lighter parafiinic raihnate fraction and a heavier extract fraction. The raihnate fraction will comprise principally parafiins including the parafiinic fraction of the condensate and the light liquid parafiinic hydrocarbons introduced into the extractor through line 39. The heavier extract fraction will be a solution of the nonparafiinic constituents of the'condensate dissolved in the nonparafiinic solvent with small amounts of paraflinic material dissolved therein, the amount of thelatter being dependent upon the relative selectivity of the nonparaflinic solti on with the vapor products withdrawn from the extract distilling chamber 41 as illustrated.

The raflinate upon being passed through either or bothof the heat exchangers 3| and 46 may be heated to a temperature sufficient to distill the solvent and the light liquid hydrocarbon antisolvent from the paraffinic fraction of the condensate. After passingthrough heat exchanger 3| the rafiinate then passes through line 48 to a distilling chamber 49 wherein the solvent and antisolvent is distilled from the parafiinic fraction of the condensate. If desired, additional heat for carrying out the distillation may be supplied directly to the distilling chamber, or the raflinate may be passed through an additional heating coil (not shown) before being introduced the solvent extractor 33, is withdrawn therefrom through line 5| and is passed through heat exchanger 30 wherein the extract is caused to pass in heat exchange relationship with the hot condensate from the bottom of the fractionating tower 25. The extract may then passthrough lines 52, 53, and 54, directly to an extract distilling chamber 41, or a portion or all of the extract may be further heated by passing through heating coil located in the top .of the bubble tower 25. The extract introduced into the extract distilling chamber 41 is subjected to distillation to vaporize the nonparafiinic solvent. If necessary,

. additional heat may be supplied directly to the (not shown) before being introduced into distilling chamber 41.

' Distillation within the ramnate distilling chamber 49 and/or the extract distilling chamber 61 may be further expedited by reducing the pressure within the respective chambers To this end the line 48, connecting heat exchanger 3! with the raflinate distilling chamber 49 may be provided with a reducing valve and the line 54, leading from the heating coil 55 to the extract distilling chamber 61, may be provided with a reducing valve 57.

It is preferred to pass the hot condensate from the bottom of the fractionating tower 25 in heat exchange with the extract from the bottom of the solvent extractor 33 in heat exchanger 36 and thereafter in heatexchange with the ramnate from the top of the extractor in heat exchanger 3! since the solvent in theextract will usually have a higher boiling point than the solvent present in the ramnate and will require a higher temperature to carry out the subsequent distillation of the solvent than that required to carry out the distillationaof the lower boiling antisolvent in the raflinate. In practice greater heat economy can be attained by passing the hot condensate from: the fractionating tower 25 first in heat exchange relation with that-fraction containing the higher boiling solvent and thereafter in heat exchange with the fraction containing the lower boiling solvent or antisolvent.

-The amount of solvent and antisolvent employed for effecting the separation will depend upon the character of the original stock, the type oi. solvent used, the temperature of extraction and the degree of separation desired, and cannot therefore be specified for all conditions. The amount and character of solvents to be used for the many different sets of conditions'have' already,

experiments.

The paramnic fraction of the condensate from which-the solvent and'antisolvent has been distilled within the distilling, chamber 69 is withthe ramnate distilling chamber 49 pass overhead I through line 62 to a condenser 68 wherein asmall amount of higher boiling nonparaflinic.

[the top' of extractor 33.

drawn from the bottom thereof through line 58 and may be returned by means of pump 56 to the inlet side of the heating coil l8 wherein it will I be subjected to further. conversion treatment with the fresh oil introduced through line it.

This paraflinic fraction mayhowever be withdrawn fromthe system through line 6i and subjected to a separate cracking operation or other treatment if desired. The vapors liberated in solvent which may have been dissolved in the rafflnate fraction is condensed." The products pass from condenser 63 to a receiving drum 64' wherein the higher boiling liquid'solvent separates from the vapors. The liquidis withdrawn from the receiving drum 86 through line 66,

- extractor 33, via line 39, but are preferably subjected to further treatment as hereinafter described. V

.The nonparamnic fraction of the condensate from which the nonparaiiinicsolvent has been distilled in chamber 41 is withdrawn from the bottom thereof through line 61, and after being cooled by heat exchange with the fresh oil for the cracking system in heat exchanger l3 as hereinbefore described, may be withdrawn from the system through line 68, or it may be subjected to further cracking or other treatment as hereinafter described. When subjected to further cracking treatment the hot extract may be bypassed around the heat exchanger I3 through line 69.

The nonparaflinic solvent vapors liberated in the extract-distilling chamber 41 pass overhead through line I I, provided with heat exchanger 46, wherein they may be used for heating the railinate fraction withdrawn from the top of the sol vent extractor 33 as hereinbefore described, and heat exchanger i2, wherein they may be used for described, to a condenser 12 (see Figure 1A).

wherein the solvent vapors .are condensed, and 4 from which the condensate passes to an accumulabor tank 13. The solvent from the accumulator tank I3 may then be returned directly to the solvent extractor 33 through line 40, or it may be introduced through line M into the upper end'of a scrubbing chamber 15 and used for scrubbing the uncondensed vapors from the receiving drum 64 which have been liberated from the ramnate fraction as before described. In the latter case the vapors from the raflinate distilling chamber 49 pass through line 62, condenser 63, condenser receiving drum 64, and line 66, to the bottom of .the scrubbing chamber 15. The vapors from receiving drum 6t, after being scrubbed by the heavier liquid nonparaflinic solvent in the scrubbing chamber 15, pass overhead through line 16- provided with pump H to the bottom section of the stabilizer 38. A by-pass line 18 connecting lines 66 and 161s provided so that the vapors from the receiving drum M may be passed directly to through'thescrubbing chamber 15. The nonparaflinic solvent, after being used for scrubbing the parafiinic solvent vapors in the scrubbing chamber 15, is withdrawn from the bottom thereof, through line l9 connecting with line 40 and is returned by means of pump to the solvent extractor 33.

As before mentioned, the vapors remaining uncondensed in the fractionating tower 25 pass overhead through line 21 to a condenser 28 (see Figure 1A) wherein the gasoline constituents are liquefied. The liquid and gaseous products from'the condenser 28 then pass to a receiving drum ill wherein fixed gases and liquid distillate separates. The-fixed gases are withdrawn from the receiver 8| through line!!! and the gasoline distillate is withdrawn from the receiving-drum Bl through line 83 provided with cheating coil 8E andis preferably passed to the stabilizer 38 wherein the gasolinev is subjected to distillation and fractionation. This stabilizer is preferably maintained under relatively high pressure and cooled at the top by pumpcback of condensed product or liquid of corresponding boiling range from another source, so that the lighter liquid hydrocarbons such as propane and butane are caused to condense at the top of the tower. Va? pors remaining uncondensed in the stabilizer i8 pass overhead through line 85 to a condenser 66 for further condensation. Liquid condensed in the condenser coil 86 passes to receiving drum 8'! and may bereturned through line 88 ,to, the upthe stabilizing column 88 without passing medium therefor. I may also introduce an additional reflux medium through line 89. The stabilizing tower 38 is preferably provided with a 90 through line III and passes to an accumulator tank 92, from which it is passed through line 39 to the lower end of the solvent extractor 33 where it is used as a solvent for carrying out the solvent separation. If desired, additional solvent for effecting this purpose may be introduced into the accumulator tank through line 93.

The gasoline freed of gases within the stabilizer 38 is withdrawn from the bottom thereof through line 90 and is passed to a suitable storage tank 95 as a final product of the system. The nonparafiinic fraction from which the solvent has been distilled within the extract distilling chamber i'I and which is Withdrawn therefrom through line 51 as hereinbefore described is preferably subjected to additional cracking or coking treatment. To this end the nonparaflinic fraction, with or without passing through heat exchanger I3, is conveyed through lines 96 and 91 bymeans of pump 98 to a separate heating coil 99 located in furnace IOI. This non-parafiinic stock is not ordinarily suitable for drastic cracking conditions such as that maintain in the heating coil I8 and it is preferred, therefore, to

maintain the heating coil 99 under more mild cracking conditions than that maintained for heating coil I8. For example, the nonparafinic fraction, during its passage through the heating coil'99, may be heated to a temperature from 800 to 900 F. and for a period of time sufficient to convert not more than of the original stock into motor fuel constituents. Furthermore, it is preferred to maintain this oil during its passage through the heating coil under relatively low pressure as compared to that in the heating coil I8. This cracking operation may for example'be maintained under cracking temperature'in which the pressure at the outlet of the coil may vary from substantially atmospheric to 200 pounds or more per square inch. The products from the heating coil 99 pass through transfer line I02 to a reaction or coking chamber I03.

In accordance with one phase of my invention the heating coil 99 and subsequent chamber I03 may be operated as a coking unit, in which case the residuum is not withdrawn continuously from the soaking chamber I03, but is allowed to remain therein until it is converted to coke. In accordance with this mode of operation, alternate chambers I03 are preferably provided so that when one chamber is filled with coke the second may be used While the first is cleaned. The vapors from chamber I03 pass overhead through line I04 to afractionating column I05. The operating conditions maintained within the chamber I03 may be such as to produce a liquid residuum rather than a solid deposit as hereinbefore described. In this event, the liquid residuum will be withdrawn from the chamber I03 through line I06. The chamber I03 is also provided with a manhole I01 for removing solid deposits, and suitable coke removing apparatus (not shown) may be used in conjunction therewith.

The vapors formed as a result of the cracking or coking operation are subjected to fractionation in the tower I05 to condense a-heavier fraction boiling above the desired endpoint of the gasoline distillate. Vapors remaining uncondensed in the fractlonating tower I05 and containing desired gasoline constituents pass overhead from the tower I05 through line I08 to a condenser coil I09 wherein the gasoline constituents are liquefied. The liquid and vapor products from the condenser coil I 09 pass to a receiving drum. III wherein the liquid distillate and fixed gases separate. The fixed gases may be withdrawn from the receiving drum III through line H2 and the gasoline distillate may be withdrawn. through line II 3. This gasoline distillate may be withdrawn from the system through line IIfi as a final product thereof, or it may be passed through line I I5 to the stabilizing tower 38 for further treatment therein. The heavier condensate fraction formed in the fractionating tower I05'is withdrawn from the bottom thereof through line H5 and ma b passing the same through heat exchanger II8 wherein it comes in heat exchange relationship with other products of the system. As shown, the hot residuum is passed in heat exchange with a part or all of the paraflinic fraction from line 58 which passes through the heat exchanger via lines H9 and I'll. This residuum, after being cooled in heat exchanger H8, may be withdrawn from the system through line I22, if so desired.

It is preferred, however, to subject a part-or all of this residuum to treatment with a liquefied, normally gaseous hydrocarbon, such as liquefied ethane, propane, or butane, or mixtures thereof to effect further separation and subject the separated components to further treatment as hereinafter described. To this end, the residuum is passed through line 23, to a mixing chamber I23,

' wherein the residuum is caused to contact with a light liquid hydrocarbon of the character above described. Additionalcracked tar from other sources may be introduced into the mixing chamber I23 through line I29 and be subjectedto additional treatment as hereinafter described. As shown, the liquefied hydrocarbons such as ethane, propane, butane, or mixtures thereof are introduced through line I25 into the mixing chamber I23. As further illustrated, this liquefied hydrocarbon may be a light product withdrawn from the upper trap-out tray 90 of the stabilizer 38 (see Figure 1A) in which case a portion of the light liquid hydrocarbon, from line 39, may be diverted through lines I 26 and I25 to the mixing chamber I23. The mixing chamber I 23 is provided with suitable mixing elements, such as baflles or stirring blades to cause an intimate mixing of the residuum and light liquid hydrocarbons. The mixture from the mixing chamber I23 passes through line I21 to a settling tank I28 wherein it separates into two temperature and pressure conditions which will retain the light hydrocarbons in liquid form." The amount of heavy lower layer precipitated by the light liquid hydrocarbon will depend upon the relative proportion of light liquid hydrocarbons used and the temperature of the separation. It is preferred to carry out the separation under conditions which will precipitates, relatively small proportion of the original residuum as a lower layer, which is suitable for coking treatment. For example, when using a iightliq uid fraction from the top of the stabilizer: 38 comprising principally propane as a separating agent equal volumes of solvent medium and residuum may be used and the separating'temperature controlled to produce an extremely heavy layer at the bottom ofthe extractor, which may comprise from to 20% of "the-residuum treated. The heavy asphaltic material separated within the settling tank I28 is withdrawn therefrom through line m9 and may be withdrawn from the system through line Isl, if so desired. In accordance with another phase of my invention, this heavy fraction from the bottom of settling tank H8 is passed through lines Q29 and M2 to the jointure of lines 96 and 91 and there combined with the extract from the bottom of the distilling. chamber at after which it is subjected to relatively mild cracking or coking treatment in heating coil 99 and chamber 803 as before described. If desired, however, this heavy fraction, or the extract fraction, may be subjected to cracking or coking treatment independently of the other fraction in heating coil 99 and chamber M3, or in a separate unit (not shown)- so that each of these fractions can be subjected to individual treatment depending upon the characteristics thereof. 1

The lighter fraction separated in the settling tank lie is withdrawn from, the top thereof through line H33 and may beiwithdrawn from the system through line I36. In accordance with another phase of my invention, however, this fraction is preferably mixed with a heavy'condensate from the bottom of fractionating tower Hi5 (see Figure 1A) and the mixture thenpassed to a solvent extraction apparatus for separating the composite stream into nic and nonparamnic constituents.

As shown in Figure 1, line it 6, leading from the bottom offractionating tower lfliiiFig'ure 1A) and'line i33fleading from the top of settling tank I28, are interconnected so that the composite stream may be passed through line J35 to the solvent extractor 83-wherein it co'mmingles I with the condensate from the bottom of the fractionating tower 25. While I have shown a common solvent extractor 83 for separating both the condensate from the fractionating tower 25 and the composite stream just mentioned into parafflnic and nonparafllnic fractions, it is understood that the composite stream may be subjected to a separate solvent extraction treatment.- When passing the lighter fraction, containing light liquid hydrocarbons, from -the top of settling tank lit-to the solventseparator 3t, relatively little or no light, liquid hydrocarbons need be introduced intothe bottom of solvent extractor 33 since the overhead from the settling tank will contain sufllcient light liquid hydrocarbons. It 7 is preferred, however, to introduce a small amount of light liquid hydrocarbons into the bottom of the extractor 88 to operate as a stripping v medium thereim The paraillnic and nonparafflnic fractions of the i composite stream separated 4 indie extractor may then e treated along "with and in the same manner as the. fractions formed from the condensate withdrawn from the 'tion, a. portion or all of the nonparaflinic frac- -pors to form a condensate and an overhead va- -ing the supernatant liq paramnic extract resulting from a solvent sep- 5 arating treatment makes an excellent water proofing, wood preserving and paving material which has remarkable penetrating properties.

In accordance with one feature of' the invention from the bottom of distilling chamber ii? is withdrawn from line 98, through line I43 and is blended, in line its and tank I65, with the heavy asphaltic fraction from the bottom of settling tank I28, withdrawn from line J32, through line M6, connecting with line M3.

Having described the preferred embodiment, it will be understood that my-invention embraces such other variations and modifications as come within the spirit and scope thereof and that it is not my intention to dedicate any novel subject matter or unnecessarily limit my invention except to distinguish from prior art.

I claim:

1. .In the pyrolytic treatment of hydrocarbon oil wherein the fresh charging oil issubjected to cracking treatment and the cracked products thereafter separatedinto vapors and unvaporlzed residuum; the improvement which comprises treating the residuum resulting from said separa-i tion with a liquefied, normally gaseous, hydro carbon to precipitate-a heavy fraction therefrom, separating said heavy fraction. from supernatant liquid, treating said-supernatant liquid with a solvent capable of separatingthe same into a paraillnic component and a nonparafllnic component and subjecting said parafflnic component to said'first mentioned cracking treatment to convert the same into hydrocarbons suitable for motor fuel.

2. In the pyrolytic conversion of hydrocarbon 011 wherein fresh charging oil is subjected ,to cracking treatment and the cracked products thereafter separated into vapors and unvaporized residue; the improvement which comprises 4 separating said heavy fraction from supernatant, 50

liquid, heating said heavy fraction so separated to a temperature and for a period sufficient to convert the same to vapors and a substantially solid residue, fractionating said last-named vapor fraction, combining said last-mentioned condensate with said supernatant liquid, treating said composite mixture with a solvent capable of. separating the same into a paraflinic fraction and a nonparafflnic fraction and subjecting said paraflinic fraction to further cracking treatment at a temperature and for a period of time sufli clent to convert the same into hydrocarbon suitable for motor fuel. 3. In the pyrolytic. conversion of hydrocarbon. oil wherein a fresh charging oil is subjected to' cracking conditions and the cracked products-1 thereafter separated into vapors and unvaporized residuum; the improvement which comprises treating the residuumgso separatedwith a liquefled, normally gaseous, hydrocarbon to precipitatea heavy fraction therefrom, separating sai heavy fraction from supernatant liquid, treat.

witha solvent Mpable of separating the sa e into a paramnic fraction and a nonparafllnic fraction, combining said nonparafiinic fraction with said heavy fracing oil is subjected to cracking treatment, the

cracked products then separated into vapors and unvaporized residue, the vapors so separated then fractionated to condense higher boiling constituents thereof from an overhead vapor fraction,

the improvement which comprises treating said last-named condensate with a solvent capable of separating the same into a parafinic fraction and a nonparafinic fraction, treating said residue with a liquid, normally gaseous, hydrocarbon to precipitate a heavy fraction therefrom, separating said heavy fraction from supernatant liquid, subjecting said nonparamnic fraction and said heavy fraction to a temperature and for a period suflicient to convert the same into vapors and a substantially solid residue.

5. In the pyrolytic treatment of hydrocarbon oil for producing motor fuel wherein higher boiling hydrocarbons are subjected to cracking conditions, the cracked products then separated into .vapors and unvaporized residue, the vapors fractionated to condense higher boiling hydrocarbons therefrom and the uncondensed vapors then subjected to a second condensing step to liquefy a final distillate product; the improvement which comprises treating said first-mentioned condensate with a solvent capable of separating the same into a parafiinic fraction and a nonparaffinic fraction, treating said residue with liquid, normally gaseous, hydrocarbons to precipitate a heavy fraction therefrom, separating said heavy fraction from supernatant liquid, combining said component and a nonparaflinic component; the

improvement which comprises treating said oil with a light liquid, normally gaseous, hydrocarbon and with a nonpara'fiinic solvent having a higher boiling point than said last-mentioned liquefied hydrocarbon, whereby the paraffinic ramnate fraction contains the light liquid normally gaseous hydrocarbon and a nonparafiinic extraction contains the nonparaihnic solvent, distilling said parafi'inic fraction to liberate said light, normally gaseous, hydrocarbons, and scrubbing the light hydrocarbons liberated from said last-named distilling operation with said nonparaffinic higher boiling solvent.

HAROLD V, ATWELL. 

